ORDER I. MACROTYPOUS L1ME-HALOIDE. 93 



high degree of heat, into a cleavable mass of rhombohedral 

 Lime-haloide, resembling saline marble. It is daily form- 

 ing in the stalactites of limestone caves and in mines, 

 where it has been observed in the Hartz, to cover the steps 

 of old ladders. A remarkable instance of its deposition in a 

 bottle of Saratoga water, has been mentioned in the Edin. 

 Phil. Journ. Vol. VIII. p. 402. 



5. Several varieties of the present species are usefully 

 employed for various purposes, partly depending upon 

 their mechanical, partly upon their chemical composition. 

 Those used in sculpture, and in ornamental architecture, 

 are called Marble, several varieties of which are celebrat- 

 ed, and their localities well known. The different kinds 

 of marble have been distinguished and denominated, and are 

 prized, according to pureness, colour, delineation, trans- 

 lucency, size of the component individuals, and of the 

 blocks which may be obtained free from fissures and ble- 

 mishes ; also according to the degree of polish they receive, 

 &c. The more common or coarse varieties are used for 

 the common purposes of building, also for paving streets. 

 A peculiar variety of very fine grained compact limestone 

 is used for plates in lithography. The best sort is found 

 near Pappenheim and Sohlenhofen in Bavaria. Quick- 

 lime mixed with sand, forms mortar ; it is also used as 

 manure, and in several manufactures, as in the process of 

 tanning, &c. Carbonic acid for chemical purposes is often 

 obtained from chalk. Chalk, and in Switzerland also Rock- 

 milk, are well known materials for writing and whitewash- 

 ing. The present species is a valuable addition in several 

 processes of melting ores, and in producing certain kinds 

 of glass ; it is particularly useful in melting iron- ores. 



3. MACROTYPOUS * LIME-HALOIDE. 

 Dolomite (in part). JAM. Syst. Vol. II. p. 462. Macro- 



* From pimps long, and rvvoi the form (fundamental form.) 



